1. Field of the Invention
The present invention relates to a driving apparatus for use in a windshield wiper of a vehicle and more particularly, a driving apparatus including a gear backlash adjusting mechanism, for use in a worm gear reduction device.
2. Description of the Related Art
Conventionally, a worm gear reduction device as shown in FIG. 11 has been used as a windshield wiper of a vehicle. In the worm gear reduction, the amount of a backlash between a gear tooth of a worm 51 and a gear tooth of a worm wheel 52 is set to approximately 0.2.about.0.3 mm. If and when the backlash amount becomes greater than the above-described amount caused by an error which has occurred in assembling the worm gear reduction device or a dimensional error of the gear teeth of the worm wheel and/or the worm which has taken place when they have been manufactured, gear teeth of the worm and the worm wheel strike against each other caused by a load which fluctuates. Thus, a noise is generated. In order to prevent the occurrence of a backlash, countermeasures for increasing a gear-manufacturing accuracy have been made and a gear selection has been also made so that the gear of the worm and the gear of the worm wheel match with each other. However, it is expensive to manufacture gears with a high accuracy and the gear selection requires much time and is troublesome. In addition, it is not easy to assemble the worm gear reduction device.